This invention relates generally to ball valves, and more particularly to a top-entry ball valve which allows for easy in-line removal of the valve seat rings and easy loading of the valve seat rings in the valve body cavity.
Heretofore, there have been devised various ball valve designs and constructions which permit the removal of the ball valve element from the valve body for replacement or repair of the seat rings. For example, U.S. Pat. No. 3,114,386 illustrates a top entry ball valve in which a cover plate is first removed and then the spring urged seats are pushed manually to a retracted position. The seat rings are then held in the retracted position by pins fitting in annular grooves of the seat rings. With the seat rings retracted, the ball is removed and then the seat rings may be released and removed from the valve body. When the valve is not installed in a flowline, a tool may be inserted through an open end of the valve body to force the seat rings to a retracted position. However, an in-line removal of the seat rings is extremely difficult because the ends of the valve are no longer accessible and the spring forces urging the seat rings toward the ball are oftentimes very powerful.
U.S. Pat. No. 4,175,577 discloses a top-entry ball valve design which permits the in-line removal of the ball and seats. In this design, the cover plate is removed and the ball partially rotated to expose its bore to the valve chamber whereby a camming tool may be inserted into the bore. Rotation of the ball to the full open position after the cam has been inserted results in the cam engaging an adjacent seat ring and urging the seat ring away from the ball. A plunger which is threadably connected to the valve body is then used to frictionally engage the seat springs to hold the seat assembly in the retracted position. An identical means and method is provided for retraction and retention of the other seat assembly such that the ball can then be removed and the seat assemblies then released for their easy removal.
A disadvantage of this design, however, is that a specially designed tool is required. Also plunger assemblies must be provided and openings formed in the valve body for their accomodation which adds to the complexity and costs of valve manufacture. In addition, with very large valves, there must be a very strong frictional contact of the plunger with the valve springs which is not always readily attainable and not always reliable.
It is therefore an object of this invention to provide a means and method for the easy and efficient in-line removal of the ball and seat rings of a ball valve.
It is also an object to provide a means for the removal of the ball and seat ring assemblies of a ball valve which does not require special tooling.
A further object is the design of a ball valve which allows for easy and quick pressure loading of the ball valve seats against the ball valve element.